Ahsan Iqbal

By definition, blood pressure is the force exerted by the blood on the walls of the blood vessels per unit area. So high blood pressure means that your blood is exerting more force per unit area on walls of your blood vessels. Most common cause of high blood pressure is atherosclerosis (normally occurs in old age). Atherosclerosis means hardening of your blood vessels, your blood vessels loose the elasticity. So when blood rushes with great velocity and force in blood vessels (especially arteries) the loss of elasticity of blood vessels prevent them to expand and in this way with less volume available, the force per unit area of blood on blood vessels is increases. I think I have made it a little complicated. Let me explain what normally happens. During systole when the heart pushes blood into arteries, the amount of blood, force behind the blood and its velocity are all greater than can be accommodated in arteries, so to accommodate the extra amount of blood, the arteries expand (and that is what is called pulse). Then during diastole, when heart is not pumping any blood, the arteries return to their normal state and the extra blood flows into circulation. This all happens too quickly, (0.8 second for all the effects to take place). So the arteries because of their elasticity, eliminate the extra force of blood but in atherosclerosis, the elasticity is lost and arteries cannot expand so not only the force per unit area is increased but the rate of flow of blood is also increased. The consequences of high blood pressure include the rupturing of blood vessels. failure of organs like the kidneys and heart failure. If you want me to explain why these occur with high blood pressure, let me know.

What is the difference between circulatory system and cardiovascular system? According to my knowledge, both are the names of same system of human body. Cardiovascular is more anatomic term and circulatory is more physiologic term. So the system to which anatomists refer as cardiovascular system, physiologists will call it circulatory system. For more details on my explanation of cardiovascular system vs. Circulatory system, see my blog post "Circulatory System vs. Cardiovascular System"

The concept of cytoskeleton = bony framework and phospholipid membrane = muscles will not apply to the case of skeleton of cells. Actually the phospho lipid membrane can be considered as a part of the skeletal system of a cell because if performs all the functions of a skeleton such as Protection, shape, stability, support etc. (in addition to its special functions). One thing you should know about cytoskeleton is that they do not give the special appearance to cell. It is the role of cell membrane. They may play a little role in the shape of cell as a whole but the role is little and cell will not get its shape without the cell membrane but it will get its shape without the cytoskeleton. The actual role of cytoskeleton is the organization of cell's internal structure and this is some times confused with shape of the cell. Organization of Cell's internal structure means that how the organelles of the cell will be distributed within the cell. The organelles remain at their position because of the cytoskeleton and thus the structure of the cell is kept organized.